columella

noun

1. Any of various small structures in plants or animals that are columnar in shape.
2. The skin at the end of the septum which separates the nostrils.
3. (comparative)In birds, reptiles, and amphibians, the small bone which carries vibration from the tympanum to the inner ear.
4. In gastropods, the structure that extends down the middle of the whorls of the shell.
5. The structure at the center of the calyx where the septa join together.
6. The central sterile portion of the sporangium in various fungi.
7. A rod-shaped reinforcing element of the sexine layer of a pollen grain.